Solid-state imaging workstations, that are configured either as vertical slot scanners each having a generally vertically arranged, upright window, or as flat-bed or horizontal slot scanners each having a generally horizontally arranged window, or as bi-optical, dual window scanners each having both generally horizontally and vertically arranged windows, have been installed in many venues, such as supermarkets, warehouse clubs, department stores, and other kinds of retailers for many years, to electro-optically read by image capture a plurality of symbol targets, such as one-dimensional symbols, particularly Universal Product Code (UPC) bar code symbols, and two-dimensional symbols, as well as non-symbol targets, such as driver's licenses, receipts, signatures, etc., the targets being associated with objects or products to be processed by the workstations. An operator or a customer may slide or swipe a product associated with, or bearing, a target in a moving direction across and past a window of the workstation in a swipe mode. Alternatively, the operator or the customer may momentarily present the target associated with, or borne by, the product to an approximate central region of a window, and steadily momentarily hold the target in front of the window, in a presentation mode. The choice depends on user preference, or on the layout of the workstation, or on the type of the target.
The symbol targets or codes have typically been printed with ink on such media as paper, foil or film labels directly applied to the products, or directly on paper, foil or film packaging that contain the products, or the printed codes have been printed remotely from the products, such as on membership or customer loyalty cards carried by customers. In recent years, it has become increasingly advantageous to display symbol targets on information display screens, such as display screens of wireless telephones (“cell phones” or “smart phones”), personal digital assistants (“PDAs”), and like mobile electronic devices, including e-readers, portable tablets, slates and computers. Displaying such symbol targets, also known as “electronic codes”, on such display screens have become increasingly desirable at such venues as airports and theaters, because they relieve consumers from needing to carry paper coded tickets and coupons.
Known imaging workstations typically include an imaging scan engine or module for supporting a solid-state, image sensor comprising an array of pixels or photosensors, for sensing return light returning through a window of the workstation from a target being imaged. The image sensor may be a one- or two-dimensional charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) device, and is analogous to the image sensors used in electronic digital cameras. The known imaging workstations also typically include an illuminating light system for illuminating the target with illumination light from an illumination light source, e.g., one or more light emitting diodes (LEDs), through the window of the workstation; an imaging lens assembly, e.g., one or more imaging lenses, for capturing return ambient and/or illumination light scattered and/or reflected from the target through the window of the workstation over a reading field of view and over a range of working distances relative to the window; and electrical circuitry for producing electronic analog signals corresponding to the intensity of the light captured by the image sensor over the reading field of view, and for digitizing the analog signal. The electrical circuitry typically includes a controller or programmed microprocessor for controlling operation of the electrical components supported by the workstations, and for processing the target and/or decoding the digitized signal based upon a specific symbology when the target is a symbol.
Some known workstations continuously capture and attempt to process and/or decode targets without regard to whether or not a target is actually in the reading field of view of the scan engine. However, continuous, repetitive, flashing of bright light from the LEDs of the illuminating light system consume and waste energy, degrade component lifetimes, and can be perceived as bothersome, distracting and annoying to the operators of the readers and to nearby consumers being served. To alleviate these problems, the known imaging workstations also typically include an object sensing system for activating the scan engine, e.g., the illuminating light system, only if an object or product bearing, or associated with, a target is detected within the active reading field of view of the scan engine. The object sensing system has one or more object light sources for emitting object sensing light, typically infrared (IR) light, and at least one object sensor for sensing the return IR light reflected and/or scattered from the object over an object detection field of view.
Although generally satisfactory for their intended purpose of reading printed codes, the known imaging workstations have not proven to be altogether satisfactory when reading the above-described electronic codes due to specular reflection of the illumination light off the display screens. Display screens can be reflective, i.e., they alter their reflectivity of ambient light to form an image, typically from light and dark pixels, such as passive black and white liquid crystal displays (“LCDs”), or can be emissive, such as backlit LCDs, i.e., they internally generate the light emitted therefrom. Whether reflective or emissive, each display screen includes a glass pane or cover, and the electronic code is displayed behind the glass pane. A portion of the illumination light incident on the glass pane is reflected therefrom back into the reading field of view of the image sensor. This reflected portion of the illumination light creates undesirable one or more hot spots in the reading field of view, at least partially and locally blinds the image sensor, and may significantly compromise reading performance. If the electronic code cannot be successfully read in a first attempt, the scan engine typically tries again and again. Often, the reading fails, and the user must take additional time to manually enter the data that would have otherwise been automatically entered into the workstation.
Accordingly, there is a need for an apparatus for, and a method of, reading both printed and electronic codes with good performance, especially by minimizing, if not eliminating, the deleterious effects of specular reflection of illumination light from a glass pane of a mobile electronic device that is displaying an electronic code.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.